Coaxial venal cannula

ABSTRACT

A dual lumen cannula includes a first tube defining a return lumen and having a proximal end, a mid-portion and a distal end, wherein the distal end includes a return aperture. A second tube is coaxial with the first tube and has a proximal end and a distal end, wherein the distal end of the second tube is fixedly attached to the mid-portion of the first tube and wherein the distal end of the second tube includes a drainage aperture. A drainage lumen is defined by a space between the first tube and the second tube. A connector is attached to the proximal end of the second tube. The connector includes a reservoir for receiving a fluid from the proximal end of the second tube. The first tube extends through the connector and does not attach directly with the second tube at the connector, and the first tube remains substantially coaxial with the second tube throughout a length of the second tube.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.12/145,738, filed Jun. 25, 2008, which claims benefit of U.S.Provisional Patent Application No. 60/946,277, filed Jun. 26, 2007. Thisapplication is also related to U.S. patent application Ser. No.12/145,763, filed Jun. 25, 2008, and U.S. patent application Ser. No.12/145,798, filed Jun. 25, 2008. The entire contents of each of theaforementioned applications are incorporated herein by reference.

BACKGROUND OF THE PRESENT INVENTION

In the past, in long term life support cases or long term extracorporealsupport cases, it has been difficult to justify the use of an externalblood circuit where a ventilator can be used. However, in cases whereventilators are used, there can be major complications and risksassociated with the use of a tracheal tube and artificial lunginflation. Artificial ventilation oftentimes has negative effectsincluding ventilator dependency and permanent scarring.

Currently, extracorporeal membrane oxygenation (“ECMO”) is used withneonatal and pediatric patients because ventilator use is not preferred.Current dual lumen cannulae for ECMO or blood circuit support cannot beused on adults because of sizing constraints, because these cannulaehave a tendency to kink, and because they can cause blood damage. Thecannulae are inserted generally in one location and are restricted intheir placement depth. Traditional cannulae used for adult life supportgenerally involve single lumen cannulae at multiple insertion sites,high volume circuits and cannulae that are not capable of long term use.Multiple sites increase the risk of bleeding, vessel damage, infection,as well as pain and discomfort to the patient. These cannulae aredesigned and built for short term acute therapies.

Therefore, a cannula that has multiple uses, includes one insertion siteand can be used for long term applications would be beneficial.

SUMMARY OF THE INVENTION

One aspect of the present invention includes a dual lumen cannulaassembly having an infusion tube defining a return lumen and having afirst outer circumference, a proximal end, and a distal end thatincludes a return aperture. A drainage tube is co-axially aligned withthe infusion tube and has a second outer circumference, a proximal endand a distal end. The distal end of the drainage tube includes adrainage site having a drainage aperture and wherein the length of thedrainage tube is less than the length of the infusion tube. A drainagelumen is defined by a space between the infusion tube and the drainagetube. A connector is attached to the proximal end of the drainage tubeand has a reservoir for receiving fluid from the proximal end of thedrainage tube, wherein the infusion tube extends through the connectorand does not attach with the drainage tube at the connector, and furtherwherein the infusion tube remains substantially coaxial with thedrainage tube throughout the length of the drainage tube.

Another aspect of the present invention includes a dual lumen cannulaassembly having an infusion tube with a distal end and a proximal end,and a drainage tube with a distal end and a proximal end. The drainagetube is co-axially aligned with the infusion tube. An improvementincludes a connector having a reservoir, a connector aperture that isfluidly connected to a mouth on a proximal end of the drainage tube, anda return opening on the connector, wherein the outside circumference ofthe infusion tube is attached to the return opening. A drainage memberis connected to the distal end of the drainage tube and furtherconnected to the outside circumference of the first small tube betweenthe proximal and distal ends of the small tube, the drainage memberincluding at least one drainage aperture. A return aperture is disposedadjacent to the distal end of the infusion tube.

Yet another aspect of the present invention includes a method of makinga cannula assembly by forming an elongate flexible infusion tube havinga proximal end and a distal end. An elongate flexible drainage tube isformed having a proximal end and a distal end. A connector is formedthat has a return opening and a connector aperture. The elongateinfusion tube is inserted into the return opening and out the connectoraperture. The infusion tube is attached to the return opening of theconnector. The distal end of the elongate return tube is connected to amid-portion of the elongate infusion tube. A drainage site having atleast one drainage aperture is installed at the distal end of theelongate return tube. An infusion site having at least one infusionaperture is installed at the distal end of the elongate infusion tube.

In another aspect of the present invention, the inside tube passesthrough the connector and is not connected internally therewith, therebyproviding a smooth, seamless transition from the blood return line tothe return aperture. Because there are no internal bond joints, welds,or connections throughout the entire extent of the return lumen, theblood that is returned to the patient's body from an ECMO circuit isdelivered without risk of damage from potential irregularities formed byinternal bond joints, welds or other forms of connection.

These and other features, advantages and objects of the presentinvention will be further understood and appreciated by those skilled inthe art upon studying the following specification, claims, and appendeddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top elevational view of one embodiment of a coaxial cannulaof the present invention inserted into the body of a patient;

FIG. 2 is a top perspective view of one embodiment of a coaxial cannulaof the present invention;

FIG. 3 is a partial enlarged top perspective view of a rear portion ofthe coaxial cannula of FIG. 2;

FIG. 4 is a partial enlarged bottom perspective view of the rear portionof the coaxial cannula of FIG. 2;

FIG. 5 is a partial enlarged side elevational view of the rear portionof the coaxial cannula of FIG. 2;

FIG. 6 is an enlarged top elevational view of the rear portion ofanother embodiment of a coaxial cannula of the present invention;

FIG. 7 is a top perspective view of the rear portion of the coaxialcannula of FIG. 6;

FIG. 8 is an enlarged top elevational view of the rear portion ofanother embodiment of a connector of a coaxial cannula of the presentinvention;

FIG. 9 is an enlarged elevational view of the rear portion of thecoaxial cannula of FIG. 8;

FIG. 10 is an enlarged rear perspective view of a coaxial cannula;

FIG. 11 is a top perspective view of the rear portion of anotherembodiment of a connector of the instant invention;

FIG. 12 is a top elevational view of one embodiment of a front portionof a coaxial cannula of the instant invention;

FIG. 13 is a top elevational view of a portion of the coaxial cannula ofFIG. 12 taken at XIII;

FIG. 14 is a top elevational view of another embodiment of a frontportion of a coaxial cannula of the instant invention;

FIG. 15 is a front perspective view of the front portion of a coaxialcannula of FIG. 14;

FIG. 16 is a top elevational view of a front portion of anotherembodiment of a coaxial cannula of the present invention;

FIG. 17 is one embodiment of a transition piece of a coaxial cannula ofthe instant invention;

FIG. 18 is a front elevational view of a coaxial cannula of the instantinvention positioned in the superior vena cava of the body of a person;

FIG. 19 is a front elevational view of a coaxial cannula of the instantinvention positioned in the inferior vena cava of the body of a person;

FIG. 20 is a front elevational view of a coaxial cannula of the instantinvention inserted through the superior vena cava and into the heart;and

FIG. 21 is a front elevational view of a coaxial cannula of the instantinvention inserted through the inferior vena cava and into the heart.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

For purposes of description herein the terms “upper”, “lower”, “right”,“left”, “rear”, “front”, “vertical”, “horizontal” and derivativesthereof shall relate to the invention as oriented in FIG. 1. However, itis to be understood that the invention may assume various alternativeorientations and step sequences, except where expressly specified to thecontrary. It is also to be understood that the specific devices andprocesses illustrated in the attached drawings, and described in thefollowing specification are simply exemplary embodiments of theinventive concepts defined in the appended claims. Hence, specificdimensions and other physical characteristics relating to theembodiments disclosed herein are not to be considered as limiting,unless the claims expressly state otherwise.

The reference numeral 10 shown in FIGS. 1-3 generally designates a duallumen cannula that includes a first infusion tube 12 having an outsidecircumference and defining an internal or return lumen 14. The firstinfusion tube 12 includes a proximal end 16, a mid-portion 18 and adistal end 20, wherein the distal end 20 includes a return aperture 22.A second drainage tube 24 is coaxial with the first tube 12 and has aproximal end 26 and a distal end 28, wherein the distal end 28 of thesecond tube 24 is fixedly attached to the mid-portion 18 of the firsttube 12 and wherein the distal end 28 is adjacent a drainage aperture30. An external or drainage lumen 32 (FIG. 3) is defined between thefirst tube 12 and the second tube 24. A connector 34 is attached to theproximal end 26 of the second tube 24, and the connector 34 includes areservoir 36 for receiving fluid from the proximal end 26 of the secondtube 24, wherein the first tube 12 extends through the connector 34 anddoes not connect with the second tube 24 at the connector 34, andwherein the first tube 12 remains substantially coaxial with the secondtube 24 throughout the length of the second tube 24.

Referring again to FIGS. 1 and 2, the extracorporeal support cannula 10has substantial placement flexibility that allows the extracorporealsupport cannula 10 to be placed in a patient at various vascularinsertion sites and depths. The extracorporeal support cannula 10 isdesigned for placement above or below the right atrium and thereforewill not typically cross the heart as disclosed below with reference toFIGS. 1, 18 and 19. Accordingly, the extracorporeal support cannula 10is less intrusive than cannulae that cross the heart. However, theextracorporeal support cannula 10 can be used to cross the heart incertain applications, as shown in FIGS. 20 and 21. The extracorporealsupport cannula 10 is adapted for use with an introducer 38 (FIG. 1)that extends through the cannula and helps the user to properly placethe extracorporeal support cannula 10 in the correct position and depthin the body of a patient. The introducer 38 may include a transitionportion 38A and extended portion 38B and a guide wire 39 extendingtherethrough. Various introducers, such as described in relatedapplication Ser. No. 12/145,763, entitled INTRODUCER FOR CANNULA ANDMETHOD, which is incorporated herein in its entirety, can be used withthe extracorporeal support cannula 10. The first or inside tube 12 andsecond or outside tube 24 are made from polyurethane, but could also bemade from PVC or silicone, and are dip molded, or extruded. Optionally,the tubes 12, 24 may be extruded and dip coated during construction.

Referring now to FIGS. 3-5, the illustrated connector 34 includes aconnector aperture 50 that is connected to the proximal end 26 of theoutside tube 24. Connector 34 also includes a return opening 52 throughwhich an inside tube 12 extends and the drainage opening 40, which isaligned with and connected to a drainage line 48. The connector aperture50 of the connector 34 is attached with a mouth 54 at the proximal end26 of the outside tube 24 and may be glued or welded thereto. Theoutside tube 24 is reinforced with a stainless steel coil 55 that wrapscircumferentially about the outside tube 24 to minimize kinking orcollapse of the extracorporeal support cannula 10. The mouth 54 of theoutside tube 24 has a larger diameter than the remainder of the outsidetube 24. This design slows down the speed of blood flow inside thecannula 10 prior to the blood reaching the ECMO apparatus, whichminimizes damage to the blood.

As shown in FIGS. 7 and 12, the distal end 28 of the outside tube 24 isbonded to the outside circumference of the inside tube 12 adjacent to adrainage site 59. The inside and outside tubes 12, 24 may directlyconnect adjacent the blood drainage site 59. Alternatively, the distalend 28 of the outside tube 24 may connect to a rearward end 56 of aseparate stiffened drainage member 57, while a forward end 58 of thedrainage member 57 connects to the outside circumference of the insidetube 12. The drainage member 57 smoothly transitions the outsidecircumference of the inside tube 12 to the outside circumference of theoutside tube 24. The inside tube 12 extends beyond the outer tube 24 andterminates proximate a blood return site 60 (FIGS. 7 and 12). The bloodreturn site 60 may include an infusion basket 61. Baskets for use indrainage and infusion of blood and which are designed for use in theextracorporeal support cannula 10 are disclosed in further detail inrelated application Ser. No. 12/145,798, entitled CANNULA REINFORCINGBAND AND METHOD, which is incorporated by reference herein in itsentirety.

Referring now to FIGS. 6 and 7, the illustrated embodiment shows theconnector 34 having a male extension portion 62. The male extensionportion 62 is adapted for insertion into a female end 64 of the drainageline 48 to allow deoxygenated blood to flow from the body of a patient,through the reservoir 36 of the connector 34 to the drainage line 48 foroxygenation in an ECMO apparatus.

The illustrated embodiment shown in FIGS. 8-10 illustrates analternative connector 34A that includes a bridge tube 66 that attachesthe connector 34A to a drainage junction 67A which is adapted forinsertion into the female end 64 of the drainage line 48. Asillustrated, the bridge tube 66 is inserted into the connector 34A andsecured to the inside of the connector 34A by adhesive or aninterference fit. The inside tube 12 extends through the connector 34Aand terminates at a drainage junction 67B which is adapted for insertioninto a female end 64 of the blood return line 46.

The illustrated example of FIG. 11 shows a connector 34B which has asimilar construction to connectors 34 and 34A outlined above, but alsoincluding an infusion extension portion 70. The infusion extensionportion 70 provides structural rigidity to the inside tube 12 as theinside tube 12 extends through the connector 34B. This arrangementminimizes the likelihood of kinking at the point where the inside tube12 extends from the connector 34B before connecting with the return line46.

Referring to FIGS. 4-12, in each of the illustrated examples, the insidetube 12 passes through the connector 34, 34A, or 34B thereby providing asmooth, seamless transition from the blood return line 46 to the returnopening 52. Joints, weldments and other connections can createirregularities in the flow of blood and can damage blood cells. Becausethere are no internal bond joints, welds, or connections throughout theentire extent of the return lumen 14, the blood that is returned to apatient's body from an ECMO apparatus is delivered without risk ofdamage from potential irregularities formed by internal bond joints,welds or other forms of connection.

The connectors 34, 34A and 34B disclosed above with respect to FIGS.6-12 are generally made from polycarbonate, but could also be made fromPVC, acrylic, or polyurethane. The connectors 34, 34A and 34B areconstructed using an operation including injection molding, machining ordip forming.

Referring again to FIGS. 7-9, the proximal end 16 of the inside tube 12receives oxygenated blood from an oxygenator (not shown) and sends itthrough a transition portion 72 (FIG. 9) that is tapered and reinforcedwith a stainless steel coil 74 that wraps circumferentially about theinside tube 12. The coil 74 as well as the coil 55 of the outside tube24 may also be made from nitinol or plastic. As the proximal end 16 ofthe inside tube 12 tapers, it enters into the return opening 52 ofconnector 34 and extends therethrough thus allowing the return lumen 14of inside tube 12 to be continuous and without bonds or joints throughthe connector 34. Depending on the application, the inside tube 12 mayor may not include structural reinforcement in a middle section 76 ofthe inside tube 12. If the middle section 76 is not reinforced, theinside tube 12 can have a thinner wall construction and consequentlybetter flow characteristics. The unreinforced middle section 76 of theinside tube 12 transitions to the distal end 20 at a blood return site60 which may be reinforced by the coil 74. Alternatively, if the middlesection 76 of the inside tube 12 is reinforced, then the inside tube 12is stronger and less susceptible to kinking or collapse of the insidetube 12.

Referring now to FIGS. 12-16, the illustrated example shows the insidetube 12 of the extracorporeal support cannula 10, which defines theinternal lumen 14. Also, as disclosed above, the external lumen 32extends through the extracorporeal support cannula 10 and is defined bythe space between the inside tube 12 and the outside tube 24. Thefunction of the internal lumen 14 is to deliver oxygenated blood to thebloodstream of a patient at a return site 60 that includes at least onereturn aperture 22. The return site 60 is located at the distal end 20of the inside tube 12. The function of the external lumen 32 is to drainblood from the bloodstream of a patient through the drainage site 59.The drainage site 59 includes multiple drainage apertures 30 that extendorthogonal to the longitudinal extent of the outside tube 24. It iscontemplated that the apertures 30 could extend at an angle relative tothe outside tube 24 and that various arrangements of drainage apertures30 could be utilized. For example, extended drainage could beincorporated wherein the drainage apertures 30 extend continuously alongthe longitudinal extent of the outside tube 24. Alternatively, thedrainage apertures 30 could be grouped into a multi-site arrangementwherein several groups of drainage apertures 30 are present along thelongitudinal extent of the outside tube 24. Advantages to thesearrangements include a shorter flow path through the ECMO circuit aswell as a lower pressure drop at the drainage site(s) 59 (the moredrainage apertures 30, the lower the pressure on the blood). It iscontemplated that the drainage apertures 30 could be oriented in any ofthe arrangements outlined above, as well as others. The drainage site 59may be located at the distal end 28 of the outside tube 24 adjacent themid-portion 18 of the first tube 12 or close to the distal end 20 of theinside tube 12.

Referring again to FIGS. 12 and 14, the return site 60 and drainagesites 59 are separated by a distance D that provides for differentamounts of mixing of oxygenated and deoxygenated blood. The distance Dcan vary according to the application, desired flow, and the size ormaturity of the patient. FIG. 12 illustrates an extended distance D thatminimizes mixing of oxygenated and deoxygenated blood during use. FIG.14 illustrates a short distance D for use in a young patient, or forlower flow rates, or in applications where mixing of oxygenated bloodand deoxygenated blood is not a critical issue.

Referring now to FIG. 16, the return site 60 includes at least onecentral return aperture 22. However, it is contemplated that additionalreturn apertures 22 may be provided that extend through the inside tube12. The return apertures 22 may be staggered or aligned and set atvarious angles relative to the longitudinal extent of the inside tube12. Additionally, a reinforcing band 61 may be installed, in the distalend 20 of the inside tube 12.

The illustrated example shown in FIG. 17, shows a transition piece 92that provides a smooth transition from the outside wall of the insidetube 12 to the drainage site 59. If the drainage site is integral withthe outside tube 24, than the transition piece 92 will abut the outsidetube 24 directly. Alternatively, if a drainage member 57 is used, thanthe transition piece 92 will abut the forward end 58 of the drainagemember 57 and taper down to and connect with the outside circumferenceof the inside tube 12. The transition piece 92 is adjacent to the distalend 28 of the outside tube 24 and is attached to the outside tube 24 andthe inside tube 12 by adhesive or may be press fit into place.

Referring to FIGS. 18 and 19, the extracorporeal support cannula 10 canbe inserted into the superior vena cava 100 or the inferior vena cava102 of the heart 104 of the patient. The introducer 38 (FIG. 1) isprovided and assists the physician in properly placing theextracorporeal support cannula 10 inside a patient's body either abovethe heart 104 (through the superior vena cava 100) or below the heart104 (through the inferior vena cava 102).

As shown in FIG. 18, when the extracorporeal support cannula 10 isinserted into the superior vena cava 100, the return site 60 is locatedbelow the drainage site 59. Accordingly, as blood flows downward fromthe superior vena cava 100 in the direction of arrow 101 toward theright atrium 106 of the heart 104, the drainage lumen 32, by way of thedrainage apertures 30, draws deoxygenated blood from the superior venacava 100, as shown by arrows 105, and sends the blood to an ECMO unit(not shown). After the blood has been oxygenated by the oxygenator, theblood flows back through the return lumen 14 out through the returnapertures 22 and into the superior vena cava 100. The blood flows backin the direction of arrows 107 into the superior vena cava 100 at thereturn site 60 which is positioned below and downstream of the drainagesite 59. As a result, the blood flowing into the heart 104 is moreoxygenated than it otherwise would be if the extracorporeal supportcannula 10 was not present. Accordingly, the lungs do not need to workas hard to oxygenate the blood, because the blood is already partiallyoxygenated, which provides some relief to the lungs.

Alternatively, as shown in FIG. 19, the extracorporeal support cannula10 can be inserted into the inferior vena cava 102 up through thefemoral vein 108. Unlike insertion into the superior vena cava 100, theextracorporeal support cannula 10 is positioned such that the returnsite 60 is located above, yet still downstream of, the drainage site 59.This is possible because the inferior vena cava 102 pumps blood upwardlyfrom the lower extremities of the body to the heart 104. As blood flowsupward through the inferior vena cava 102 in the direction of arrow 103toward the right atrium 106 of the heart 104, the drainage lumen 32, byway of the drainage aperture(s) 30, draws deoxygenated blood from theinferior vena cava 102, as indicated by arrows 109, and sends thedeoxygenated blood to the ECMO unit. After the blood has beenoxygenated, the blood flows back through the return lumen 14 out throughthe return aperture(s) 22 and into the inferior vena cava 102. As statedabove, the blood flows back into the inferior vena cava 102 from thereturn site 60 at a position above the drainage site 59, as indicated byarrows 111. Consequently, the blood flowing into the heart 104 is moreoxygenated than it otherwise would be if the extracorporeal supportcannula 10 was not present. Accordingly, the lungs do not need to workas hard to oxygenate the blood, providing some relief to that organ.

In either of the applications described above (insertion through theinferior vena cava 102 or through the superior vena cava 100) as shownin FIGS. 18 and 19, the extracorporeal support cannula 10 can be used toprovide partial or complete carbon dioxide removal as well as partial orcomplete oxygen addition. In both carbon dioxide removal as well asoxygen addition, the extracorporeal support cannula 10 can be used inlong term or short term applications. The extracorporeal support cannula10 is also designed for use in hemofiltration purposes including renaldialysis and hepatic applications. In addition, the extracorporealsupport cannula 10 can be used for blood heat exchange applications toelevate or lower the temperature of the blood. These applicationsinclude hyperthermia therapy and re-warming purposes when a patient issuffering from hypothermia. The extracorporeal support cannula 10 canalso be used in venovenous lung support or life support in cases wherenormal lung function is lessened or recovery time is required. Further,it is contemplated that extracorporeal support cannula 10 can be used inleft heart (aortic) applications as well as abdominal aorticapplications.

Another possible application for the extracorporeal support cannula 10includes providing offload support to the right ventricle 110 of theheart 104. To assist the right ventricle 110 from above the heart 104,the extracorporeal support cannula 10 is first inserted through apatient's superior vena cava 100 and into the right atrium 106. Thereturn site 60 of the extracorporeal support cannula 10 is then gentlypushed through tricuspid valve 112 and into the right ventricle 114. Thereturn site 60 is then gently eased through the pulmonary valve 116 andinto the pulmonary artery 118. In this position, the drainage site 59 ofthe extracorporeal support cannula 10 is positioned in the superior venacava 100 or possibly right atrium 106. Deoxygenated blood is drawn fromthe superior vena cava 100 or right atrium 106 as indicated by arrows120 and oxygenated by an ECMO apparatus. The oxygenated blood is thenreturned to the pulmonary artery 118 through the return lumen 14 outthrough the return apertures 22 at the return site 60 as indicated byarrows 122, following the direction of the flow of blood, as shown byarrow 124. This positioning of the extracorporeal support cannula 10 ishelpful in cases where the right ventricle 114 is not strong enough tohandle full body blood volume.

Alternatively, as shown in FIG. 21, the extracorporeal support cannula10 may be inserted into the inferior vena cava 102 and into the rightatrium 106. The extracorporeal support cannula 10 is then turned topenetrate past the tricuspid valve 112 thereby entering the rightventricle 114. The return site 60 is then eased past the pulmonary valve116 and into the pulmonary artery 118. As deoxygenated blood flows upfrom the inferior vena cava 102 into the right atrium 106, deoxygenatedblood is drained from the inferior vena cava 102 or right atrium 106 andoxygenated in an ECMO apparatus, as indicated by arrows 126. Theoxygenated blood is then returned to the pulmonary artery 118 throughthe return apertures 22 of the return site 60, as shown by arrows 128,following the direction of the flow of blood designated by arrow 124.

The above description is considered that of the preferred embodimentsonly.

Modifications of the invention will occur to those skilled in the artand to those who make or use the invention. Therefore, it is understoodthat the embodiments shown in the drawings and described above is merelyfor illustrative purposes and not intended to limit the scope of theinvention, which is defined by the following claims as interpretedaccording to the principles of patent law, including the Doctrine ofEquivalents.

What is claimed is:
 1. A dual lumen cannula assembly, comprising: aninfusion tube defining a return lumen and having a first outercircumference, a proximal end, and a distal end that includes a returnaperture, at least a portion of said infusion tube includes a wallhaving a reinforcing coil.; a drainage tube co-axially aligned with saidinfusion tube and having a second outer circumference, a proximal endand a distal end, wherein said distal end of said drainage tube includesa drainage site having a drainage aperture, and wherein a length of saiddrainage tube is less than a length of said infusion tube, wherein: saiddrainage site includes a drainage member having first and second ends,said first end is attached to said distal end of said drainage tube, andsaid second end is attached to the first outer circumference of saidinfusion tube; a drainage lumen defined by a space between said infusiontube and said drainage tube; and a connector attached to said proximalend of said drainage tube and comprising a reservoir for receiving fluidfrom said proximal end of said drainage tube and a return opening thatis attached to said proximal end of said infusion tube, wherein: saidinfusion tube extends through said connector and does not attach withsaid drainage tube at said connector, and said infusion tube remainssubstantially coaxial with said drainage tube throughout the length ofsaid drainage tube.
 2. The dual lumen cannula assembly of claim 1,further comprising an infusion basket disposed on said distal end ofsaid infusion tube.
 3. The dual lumen cannula assembly of claim 2,further comprising a transition piece adjacent said drainage site andconnected to the first outer circumference of said infusion tube.
 4. Thedual lumen cannula assembly of claim 3, further comprising an introduceradapted for insertion into said return lumen of said infusion tube.
 5. Adual lumen cannula assembly, comprising: an infusion tube with a distalend and a proximal end, a drainage tube with a distal end and a proximalend, wherein the drainage tube is co-axially aligned with the infusiontube; a connector having a reservoir, a connector aperture that isfluidly connected to a mouth on a proximal end of said drainage tube,and a return opening on said connector, wherein an outer circumferenceof said infusion tube is attached to said return opening; a drainagemember connected to said distal end of said drainage tube and furtherconnected to an outer circumference of said infusion tube between saidproximal and distal ends of said infusion tube, said drainage memberincluding at least one drainage aperture; and a return aperture disposedadjacent to said distal end of said infusion tube.
 6. A method of makinga cannula assembly, the method comprising: forming an elongate flexibleinfusion tube having a proximal end and a distal end; forming anelongate flexible drainage tube having a proximal end and a distal end;forming a connector having a return opening, and a connector aperture;inserting said elongate infusion tube into said return opening and outsaid connector aperture; attaching said infusion tube to said returnopening of said connector; connecting a distal end of said elongatedrainage tube to a mid-portion of said elongate infusion tube;installing a drainage site having at least one drainage aperture at saiddistal end of said elongate drainage tube; and installing an infusionsite having at least one infusion aperture at said distal end of saidelongate infusion tube.
 7. The method of claim 6, further comprisinginstalling a reinforcing coil in a wall of said drainage tube.
 8. Themethod of claim 6, further comprising installing a reinforcing coil in awall of said infusion tube.
 9. The method of claim 6, further comprisinginstalling a reservoir in said connector fluidly connected to a mouth onsaid drainage tube.